The invention relates to an electric sauna oven comprising at least one electric resistor for heating the oven, means for supplying current to said at least one electric resistor, and thermostatic means and temperature limiting means for controlling the supply of current to said at least one resistor.
For some years it was customary to position the detecting means of the thermostat and the temperature limiter of an electric sauna oven on the wall of the sauna at a suitable height to directly measure the temperature in the sauna room. A more recent tendency has been to get rid of this way of installation because it requires rather long wirings when installing the oven. At present the detecting means of the thermostat and temperature limiter are in most cases installed within the outer jacket of the oven to measure the temperature of the air streaming between the jackets. Thus the installation can be completed at the factory. Since it is the temperature of the air streaming between the jackets of the oven that is to be measured, attempts have been made to separate the detecting means from the other structures of the oven to the extent possible. This has been effected firstly by arranging a reflector, such as an aluminum film, on the inner surface of the stone space beside the detecting means in order to reflect thermal radiation away therefrom. Secondly, the detecting means have been placed on a fairly light holder so that the heat transferred from the jackets through conduction would not affect the detecting means.
In other words, the operation of traditional electric sauna ovens has been tried to be controlled on the basis of the temperature of the air contained in the steam room. This, however, has led to an obvious risk of the ceiling structures of the sauna room being overheated, particularly during the initial heating of the oven. For example, if the set value of the thermostat is about 120.degree. C., then the temperature of the ceiling structures will exceed the allowed value, i.e. 140.degree. C., during the initial heating. As a result of this, it has been necessary to limit the temperatures of the sauna room in order to prevent the overheating of the ceiling structures. The slowness of the adjustment based on the measurements of the temperature of air can be regarded as a major reason for this overheating. On the other hand, the overheating of the ceiling structures has been tried to be avoided by the use of oven structures in which the amount of the air flowing therethrough has been as large as possible. Consequently, the temperature of the oven stones might drop very near the temperature of the steam room at the beginning of the sauna bath if the oven has been left waiting for some time after the initial heating thereof, and this has considerably decreased the steam generating capacity of the stones.